Some lawn mowers are configured to contain: a work unit including a housing provided in a lower part of a main body to have a downward-facing opening and a cutter blade rotatably provided in the housing; a grass clippings receptacle for receiving grass clippings cut by the work unit; a grass clippings transport passage connecting an interior of the housing with the grass clippings receptacle; and a shutter manually operable to selectively open and close the grass clippings transport passage (see JP2014-60936A, for example). When rotated, the cutter blade cuts the grass and generates a transport air flow flowing from the opening of the housing to inside. When the shutter is open, the grass clippings are carried by the transport air flow through the grass clippings transport passage and collected in the grass clippings receptacle (bagging mode), and when the shutter is closed, the grass clippings are discharged onto the ground from the opening of the housing (mulching mode).
In such a lawn mower, a full-state sensor for detecting a full state of the grass clippings receptacle based on a height or a weight of the grass clippings contained in the grass clippings receptacle may be provided, so that when the full state of the grass clippings receptacle is detected, an operator is prompted by means of a display or the like to switch from the bagging mode to the mulching mode to prevent clogging of the grass clippings receptacle and the grass clippings transport passage. However, the grass clippings transport passage can be clogged before the grass clippings receptacle becomes full, and in such a case, the full-state sensor cannot effectively detect clogging of the grass clippings transport passage. If the grass clippings transport passage is clogged up heavily, it is troublesome for the operator to remove the grass clippings from the grass clippings transport passage.